What do you recommend and why?

Lightspeed is faster, but Apache is free.

Lightspeed all the way. You'll get 2 to 3 times better performance, but it does require a little extra hand holding (and money). But if you're running busy sites, it's worth every penny.

Litespeed.

more memory foot-print, CGI Performance enhancement in litespeed, built-in DDOS protection, built-in load balancer module etc.

Lightspeed is faster and works great for handling huge doss attack without causing server crashes. Whereas Apache is limited to handle small doss attack but when its comes to huge doss attack their might be risk of server crashes.

LiteSpeed is better for handling high traffic sites, however if you are running a general site Apache is great just need to configure it to your needs and presto.

I love Apache as I am familiar with it. LiteSpeed is better and fast but not free to use.

Apache: free and I love all it's module addons and cofiguration system.
Try it in a LAMP system with webmin open source control panel and you'll see all the power of apache!

As everyone else said, if you got the $$ go with litespeed. Its faster. Apache is free, and fits the requirements of most people.

Currently, we offer a special reseller package with LiteSpeed, but we don't use it ourselves. The main reason is that I don't like to support companies that impose their morals on their users (read their ToS). After some reflection, I will probably not sell it either to be consistent.

Back to the matter at hand, we use Apache for everything at this point, but I am compiling a list of the many different web servers with the hopes of testing and benchmarking them all.

hmm... i know that litespeed is very speed, this the main point of the lite speed BUT Apache: free and safe, are you know that lite speed cannot build up better to use it for WP or joomla to design?

Sorry but did you know WordPress.org and WordPress.com are powered by LiteSpeed?
Yes LiteSpeed is not free to use but it is really good.

Litespeed is good but apache is free

nginx is a pretty damn fast and free http server. We have lots of clients using it for large sites.

http://uptime.netcraft.com/up/graph?site=wordpress.com

As mentioned earlier, WordPress.com has made the move from Litespeed for their frontend serving needs to Nginx, the little lightning fast server from Russia. Matt had mentioned that they were quite happy with LiteSpeed, but wanted to move to something else purely to have their entire stack run with open sourced software.

It is a huge boost for Nginx, which has in any case been growing at a rapid pace in terms of adoption in the recent years, especially as a reverse proxying solutin for the Ruby On Rails crowd. What is quite interesting is that WordPress.com is running the development version of the software (0.6.29) than the stable one (0.5.35). There is, though, no clarity if Nginx is being used purely as a reverse proxying solution for WordPress.com, or if it is actually serving PHP too though the FCGI route.